Nonacidic multimetallic catalytic composite

ABSTRACT

Dehydrogenatable hydrocarbons are dehydrogenated by contacting them, at dehydrogenation conditions, with a catalytic composite comprising a combination of catalytically effective amounts of a platinum group component, a Group IV-A metallic component, and a Group VI-B transition metal component with a porous carrier material. A specific example of the nonacidic catalytic composite disclosed herein is a combination of platinum group component, a Group IV-A metallic component, a Group VI-B component, and an alkali or alkaline earth component with a porous carrier material; wherein the components are uniformly dispersed throughout the porous carrier material; wherein substantially all of the platinum group component is present therein in the elemental metallic state and substantially all of the Group IV-A metallic component, the Group VI-B component and the alkali or alkaline earth component are present therein in an oxidation state above the elemental metal; wherein the composite contains, on an elemental basis, about 0.01 to about 2 wt. % platinum group metal, about 0.01 to about 5 wt. % Group IV-A metal, about 0.01 to 3 wt. % Group VI-B metal, about 0.1 to about 5 wt. % alkali metal or alkaline earth metal; and wherein the atomic ratio of Group VI-B metal to platinum group metal is about 0.05:1 to about 4:1.

CROSS-REFERENCES TO RELATED APPLICATIONS

This applicaton is a division of my prior, copending application Ser.No. 642,648 filed Dec. 19, 1975, now U.S. Pat. No. 4,072,602, issuedFeb. 7, 1978; which in turn is a continuation-in-part of my priorapplicaion Ser. No. 442,714 filed Feb. 14, 1974 and issued on Dec. 23,1975 as U.S. Pat. No. 3,928,177; which in turn is a continuation-in-partof my prior application Ser. No. 216,739 filed Jan. 10, 1972 and issuedon Apr. 23, 1974 as U.S. Pat. No. 3,806,446; and which in turn is adivision of my prior, now abandoned application Ser. No. 17,886 filedMar. 9, 1970. All of the teachings of these prior applications arespecifically incorporated herein by reference.

The subject of the present invention is, broadly, an improved method fordehydrogenating a dehydrogenatable hydrocarbon to produce a hydrocarbonproduct containing the same number of carbon atoms but fewer hydrogenatoms. In another aspect, the present invention involves a method ofdehydrogenating normal paraffin hydrocarbons containing 4 to 30 carbonatoms per molecule to the corresponding normal mono-olefin with minimumproduction of side products. In yet another aspect, the presentinvention relates to a novel nonacidic multimetallic catalytic compositecomprising a combination of catalytically effective amounts of aplatinum group component, a Group IV-A metallic component, a Group VI-Btransition metal component, and an alkali or alkaline earth componentwith a porous carrier material. This nonacidic composite has highlybeneficial characteristics of activity, selectivity, and stability whenit is employed in the dehydrogenation of dehydrogenatable hydrocarbonssuch as aliphatic hydrocarbons, naphthene hydrocarbons, andalkylaromatic hydrocarbons.

The conception of the present invention followed from my search for anovel catalytic composite possessing a hydrogenation-dehydrogenationfunction, a controllable cracking function, and superior conversion,selectivity, and stability characteristics when employed in hydrocarbonconversion processes that have traditionally utilized dual-functioncatalytic composites. In my prior applicatons, I disclosed a significantfinding with respect to a multimetallic catalytic composite meetingthese requirements. More specifically, I determined that a combinationof specified amounts of a Group IV-A component and a Group VI-Bcomponent can be utilized, under certain conditions, to beneficiallyinteract with the platinum group component of a dual-function catalystwith a resulting marked improvement in the performance of such acatalyst. Now I have ascertained that a catalytic composite, comprisinga combination of catalytically effective amounts of a platinum groupcomponent, a Group IV-A metallic component, and a Group VI-B transitionmetal component with a porous carrier material can have superioractivity, selectivity, and stability characteristics when it is employedin a dehydrogenation process if these components are uniformly dispersedin the porous carrier material in the amounts specified hereinafter andif the oxidation state of the metallic ingredients are carefullycontrolled so that substantially all of the platinum group component ispresent in the elemental metallic state and substantially all of theGroup IV-A and Group VI-B components are present in an oxidation stateabove that of the elemental metal. Moreover, I have discerned that aparticularly preferred multimetallic catalytic composite of this typecontains not only a platinum group component, a Group IV-A metalliccomponent, and a Group VI-B component, but also an alkali or alkalineearth component in an amount sufficient to ensure that the resultingcatalyst is nonacidic.

The dehydrogenation of dehydrogenatable hydrocarbons is an importantcommercial process because of the great and expanding demand fordehydrogenated hydrocarbons for use in the manufacture of variouschemical products such as detergents, plastics, synthetic rubbers,pharmaceutical products, high octane gasoline, perfumes, drying oils,ion-exchange resins, and various other products well know to thoseskilled in the art. One example of this demand is in the manufacture ofhigh octane gasoline by using C₃ and C₄ mono-olefins to alkylateisobutane. Another example of this demand is in the area ofdehydrogenation of normal paraffin hydrocarbons to produce normalmono-olefins having 4 to 30 carbon atoms per molecule. These normalmono-olefins can, in turn, be utilized in the synthesis of a vast numberof other chemical products. For example, derivatives of normalmono-olefins have become of substantial importance to the detergentindustry where they are utilized to alkylate an aromatic, such asbenzene, with subsequent transformation of the product arylalkane into awide variety of biodegradable detergents such as the alkylaryl sulfonatetypes of detergents which are most widely used today for household,industrial, and commercial purposes. Still another large class ofdetergents produced from these normal mono-olefins are the oxyalkylatedphenol derivatives in which the alkyl phenol base is prepared by thealkylation of phenol with these mono-olefins. Still another type ofdetergents produced from these normal mono-olefins are the biodegradablealkylsulfonates formed by the direct sulfation of the normalmono-olefins. Likewise, the olefin can be subjected to directsulfonation with sodium bisulfite to make biodegradable alkylsulfonates.As a further example, these mono-olefins can be hydrated to producealcohols which then, in turn, can be used to produce plasticizers and/orsynthetic lube oils.

Regarding the use of products made by the dehydrogenation ofalkylaromatic hydrocarbons, they find wide application in the petroleum,petrochemical, pharmaceutical, detergent, plastic, and the likeindustries. For example, ethylbenzene is dehydrogenated to producestyrene which is utilized in the manufacture of polystyrene plastics,styrene-butadiene rubber, and the like products. Isopropylbenzene isdehydrogenated to form alpha-methylstyrene which, in turn, isextensively used in polymer formation and in the manufacture of dryingoils, ion exchange resins, and the like materials.

Responsive to this demand for these dehydrogenation products, the arthas developed a number of alternative methods to produce them incommercial quantities. One method that is widely utilized involves theselective dehydrogenation of a dehydrogenatable hydrocarbon bycontacting the hydrocarbon with a suitable catalyst at dehydrogenationconditions. As is the case with most catalytic procedures, the principalmeasure of effectiveness for this dehydrogenation method involves theability to perform its intended function with minimum interference ofside reactions for extended periods of time. The analytical terms usedin the art to broadly measure how well a particular catalyst performsits intended functions in a particular hydrocarbon conversion reactionare activity, selectivity, and stability, and for purposes of discussionhere, these terms are generally defined for a given reactant as follows:(1) activity is a measure of the catalyst's ability to convert thehydrocarbon reactant into products at a specified severity level whereseverity level means the specific reaction conditions used--that is, thetemperature, pressure, contact time, and presence of diluents such as H₂; (2) selectivity usually refers to the amount of desired product orproducts obtained relative to the amount of the reactant charged orconverted; (3) stability refers to the rate of change with time of theactivity and selectivity parameters--obviously the smaller rate implyingthe more stable catalyst. More specifically, in a dehydrogenationprocess, activity commonly refers to the amount of conversion that takesplace for a given dehydrogenatable hydrocarbon at a specified severitylevel and is typically measured on the basis of disappearance of thedehydrogenatable hydrocarbon; selectivity is typically measured by theamount, calculated on a mole percent of converted dehydrogenatablehydrocarbon basis, of the desired dehydrogenated hydrocarbon obtained atthe particular activity or severity level; and stability is typicallyequated to the rate of change with time of activity as measured bydisappearance of the dehydrogenatable hydrocarbon and of selectivity asmeasured by the amount of desired dehydrogenated hydrocarbon produced.Accordingly, the major problem facing workers in the hydrocarbondehydrogenation art is the development of a more active and selectivecatalytic composite that has good stability characteristics.

I have now found a multimetallic catalytic composite which possessesimproved activity, selectivity, and stability when it is employed in aprocess for the dehydrogenation of dehydrogenatable hydrocarbons. Inparticular, I have determined that the use of a multimetallic catalyst,comprising a combination of catalytically effective amounts of aplatinum group component, a Group IV-A metallic component, and a GroupVI-B transition metal component with a porous refractory carriermaterial, can enable the performance of a dehydrogenation process to besubstantially improved if the metallic components are uniformlydispersed throughout the carrier material in the amounts and relativerelationships specified hereinafter and if their oxidation states arecarefully controlled to be in the states hereinafter specified.Moreover, particularly good results are obtained when this composite iscombined with an amount of an alkali or alkaline earth componentsufficient to ensure that the resulting catalyst is nonacidic andutilized to produce dehydrogenated hydrocarbons containing the samecarbon structure as the reactant hydrocarbon but fewer hydrogen atoms.This nonacidic multimetallic catalytic composite is particularly usefulin the dehydrogenation of long chain normal paraffins to produce thecorresponding normal mono-olefin with minimization of side reactionssuch as skeletal isomerization, aromatization, cracking and polyolefinformation.

In sum, the current invention involves the significant finding that acombination of a Group IV-A component and a Group VI-B component can beutilized under the circumstances specified herein to beneficiallyinteract with and promote a dehydrogenation catalyst containing aplatinum group metal.

It is, accordingly, one object of the present invention to provide anovel method for the dehydrogenation of dehydrogenatable hydrocarbonsutilizing a multimetallic catalytic composite comprising catalyticallyeffective amounts of a platinum group component, a Group IV-A metalliccomponent, and a Group VI-B transition metal component combined with aporous carrier material. A second object is to provide a novel nonacidiccatalytic composite having superior performance characteristics whenutilized in a dehydrogenation process. Another object is to provide animproved method for the dehydrogenation of normal paraffin hydrocarbonsto produce normal mono-olefins which method minimizes undesirable sidereactions such as cracking, skeletal isomerization, polyolefin formationand aromatization.

In brief summary, one embodiment of the present invention involves amethod for dehydrogenating a dehydrogenatable hydrocarbon whichcomprises contacting the hydrocarbon at dehydrogenation conditions witha multimetallic catalytic composite comprising a porous carrier materialcontaining a uniform dispersion of catalytically effective amounts of aplatinum group component, a Group IV-A metallic component, and a GroupVI-B transition metal component. Moreover, substantially all of theplatinum group component is present in the composite in the elementalmetallic state and substantially all of the Group IV-A component andGroup VI-B component are present in an oxidation state above that of theelemental metal. Further, these components are present in this compositein amounts, calculated on an elemental basis, sufficient to result inthe composite containing about 0.01 to about 2 wt. % platinum groupmetal, about 0.01 to about 5 wt. % Group IV-A metal, about 0.01 to about3 wt. % Group VI-B transition metal, and an atomic ratio of Group VI-Bmetal to platinum group metal of about 0.05:1 to about 4:1.

A second embodiment relates to the dehydrogenation method described inthe first embodiment wherein the dehydrogenatable hydrocarbon is analiphatic compound containing 2 to 30 carbon atoms per molecule.

A third embodiment comprehends a nonacidic catalytic compositecomprising a porous carrier material having uniformly dispersed thereincatalytically effective amounts of a platinum group component, a GroupIV-A metallic component, a Group VI-B transition metal component, and analkali or alkaline earth component. These components are preferablypresent in amounts sufficient to result in the catalytic compositecontaining, on an elemental basis, about 0.01 to about 2 wt. % platinumgroup metal, about 0.1 to about 5 wt. % of the alkali metal or alkalineearth metal, about 0.01 to about 5 wt. % Group IV-A metal, about 0.01 toabout 3 wt. % Group VI-B transition metal, and an atomic ratio of GroupVI-B to platinum group metal of about 0.05:1 to about 4:1. In addition,substantially all of the platinum group component is present in theelemental metallic state, and substantially all of the Group IV-A, GroupVI-B and alkali or alkaline earth components are present in an oxidationstate above that of the elemental metal.

Another embodiment pertains to a method for dehydrogenating adehydrogenatable hydrocarbon which comprises contacting the hydrocarbonwith the catalytic composite described in the third embodiment atdehydrogenation conditions.

Other objects and embodiments of the present invention involve specificdetails regarding essential and preferred catalytic ingredients,preferred amounts of ingredients, suitable methods of multimetalliccomposite preparation, suitable dehydrogenatable hydrocarbons, operatingconditions for use in the dehydrogenation process, and the likeparticulars. These are hereinafter given in the following detaileddiscussion of each of these factors of the present invention. It is tobe noted that the term "nonacidic" means that the catalyst produces lessthan 10% conversion of 1-butene to isobutylene when tested atdehydrogenation conditions and, preferably, less than 1%.

Regarding the dehydrogenatable hydrocarbon that is subjected to themethod of the present invention, it can, in general, be an organiccompound having 2 to 30 carbon atoms per molecule and containing atleast 1 pair of adjacent carbon atoms having hydrogen attached thereto.That is, it is intended to include within the scope of the presentinvention, the dehydrogenation of any organic compound capable of beingdehydrogenated to produce products containing the same number of carbonatoms but fewer hydrogen atoms, and capable of being vaporized at thedehydrogenation temperatures used herein. More particularly, suitabledehydrogenatable hydrocarbons are: aliphatic compounds containing 2 to30 carbon atoms per molecule, alkylaromatic hydrocarbons where the alkylgroup contains 2 to 6 carbon atoms, and naphthenes or alkyl-substitutednaphthenes. Specific examples of suitable dehydrogenatable hydrocarbonsare: (1) alkanes such as ethanes, propane, n-butane, isobutane,n-pentane, isopentane, n-hexane, 2-methylhexane, 2-methylpentane,2,2-dimethylbutane, n-heptane, 2-methylhexane, 2,2,3-trimethylbutane,and the like compounds; (2) naphthenes such as cyclopentane,cyclohexane, methylcyclopentane, ethylcyclopentane,n-propylcyclopentane, 1,3-dimethylcyclohexane, and the like compounds;and (3) alkylaromatics such as ethylbenzene, n-butylbenzene,1,3,5-triethylbenzene, isopropylbenzene, isobutylbenzene,ethylnaphthalene, and the like compounds.

In a preferred embodiment, the dehydrogenatable hydrocarbon is a normalparaffin hydrocarbon having about 4 to 30 carbon atoms per molecule. Forexample, normal paraffin hydrocarbons containing about 10 to 18 carbonatoms per molecule are dehydrogenated by the subject method to producethe corresponding normal mono-olefin which can, in turn, be alkylatedwith benzene and sulfonated to make alkylbenzene sulfonate detergentshaving superior biodegradability. Likewise, n-alkanes having 10 to 18carbon atoms per molecule can be dehydrogenated to the correspondingnormal mono-olefin which, in turn, can be sulfonated or sulfated to makeexcellent detergents. Similarly, n-alkanes having 6 to 10 carbon atomscan be dehydrogenated to form the corresponding mono-olefin which can,in turn, be hydrated to produce valuable alcohols. Preferred feedstreams for the manufacture of detergent intermediates contain a mixtureof 4 or 5 adjacent normal paraffin homologues such as C₁₀ to C₁₃, C₁₁ toC₁₄, C₁₁ to C₁₅ and the like mixtures.

The multimetallic catalyst used in the present invention comprises aporous carrier material or support having combined therewith a uniformdispersion of catalytically effective amounts of a platinum groupcomponent, a Group IV-A metallic component, a Group VI-B transitionmetal component, and, in the preferred case, an alkali or alkaline earthcomponent.

Considering first the porous carrier material utilized in the presentinvention, it is preferred that the material be a porous, adsorptive,high-surface area support having a surface area of about 25 to about 500m² /g. The porous carrier material should be relatively refractory tothe conditions utilized in the dehydrogenation process, and it isintended to include within the scope of the present invention carriermaterials which have traditionally been utilized in dual-functionhydrocarbon conversion catalysts, such as: (1) activated carbon, coke,charcoal; (2) silica or silica gel, silicon carbide, clays, andsilicates including those synthetically prepared and naturallyoccurring, which may or may not be acid treated, for example, attapulgusclay, china clay, diatomaceous earth, fuller's earth, kaolin,kiesel-guhr, etc.; (3) ceramics, porcelain, crushed firebrick, bauxite;(4) refractory inorganic oxides such as alumina, titanium dioxide,zirconium dioxide, chromium oxide, zinc oxide, magnesia, thoria, boria,silica-alumina, silica-magnesia, chromia-alumina, alumina-boria,silica-zirconia, etc.; (5) crystalline zeolitic aluminosilicates such asnaturally occurring or synthetically prepared mordenite and/orfaujasite, either in the hydrogen form or in a form which has beentreated with multivalent cations, (6) spinels such as MgAl₂ O₄, FeAl₂O₄, ZnAl₂ O₄, MnAl₂ O₄, CaAl₂ O₄, and other like compounds having theformula MO.Al₂ O₃ where M is a metal having a valence of 2; and (7)combinations of elements from one or more of these groups. The preferredporous carrier materials for use in the present invention are refractoryinorganic oxides, with best results obtained with an alumina carriermaterial. Suitable alumina materials are the crystalline aluminas knownas the gamma-, eta-, and theta-alumina, with gamma- or eta-aluminagiving best results. In addition, in some embodiments the aluminacarrier material may contain minor proportions of other well-knownrefractory inorganic oxides such as silica, zirconia, magnesia, etc.;however, the preferred support is substantially pure gamma- oreta-alumina. Preferred carrier materials have an apparent bulk densityof about 0.2 to about 0.7 g/cc and surface area characteristics suchthat the average pore diameter is about 20 to about 300 Angstroms, thepore volume is about 0.1 to about 1 cc/g and the surface area is about100 to about 500 m² /g. In general, best results are typically obtainedwith a gamma-alumina carrier material which is used in the form ofspherical particles having: a relatively small diameter (i.e. typicallyabout 1/16 inch), an apparent bulk density of about 0.2 to about 0.6(most preferably about 0.3) g/cc, a pore volume of about 0.4 cc/g, and asurface area of about 150 to about 200 m² /g.

The preferred alumina carrier material may be prepared in any suitablemanner and may be synthetically prepared or natural occurring. Whatevertype of alumina is employed, it may be activated prior to use by one ormore treatments including drying, calcination, steaming, etc., and itmay be in a form known as activated alumina, activated alumina ofcommerce, porous alumina, alumina gel, etc. For example, the aluminacarrier may be prepared by adding a suitable alkaline reagent, such asammonium hydroxide to a salt of aluminum such as aluminum chloride,aluminum nitrate, etc., in an amount to form an aluminum hydroxide gelwhich upon drying and calcining is converted to alumina. The aluminacarrier may be formed in any desired shape such as spheres, pills,cakes, extrudates, powders, granules, etc., and utilized in any desiredsize. For the purpose of the present invention, a particularly preferredform of alumina is the sphere; and alumina spheres may be continuouslymanufactured by the well-known oil drop method which comprises: formingan alumina hydrosol by any of the techniques taught in the art andpreferably by reacting aluminum metal with hydrochloric acid, combiningthe resulting hydrosol with a suitable gelling agent and dropping theresultant mixture into an oil bath maintained at elevated temperatures.The droplets of the mixture remain in the oil bath until they set andform hydrogel spheres. The spheres are then continuously withdrawn fromthe oil bath and typically subjected to specific aging treatments in oiland an ammoniacal solution to further improve their physicalcharacteristics. The resulting aged and gelled particles are then washedand dried at a relatively low temperature of about 300° F. to about 400°F. and subjected to a calcination procedure at a temperature of about850° F. to about 1300° F. for a period of about 1 to about 20 hours. Itis a good practice to subject the calcined particles to a hightemperature treatment with steam in order to remove undesired acidiccomponents such as residual chloride. This procedure effects conversionof the alumina hydrogel to the corresponding crystalline gamma-alumina.See the teachings of U.S. Pat. No. 2,620,314 for additional details.

One essential constituent of the instant multimetallic catalyticcomposite is the Group IV-A metallic component. By the use of thegeneric term "Group IV-A metallic component" it is intended to cover themetals of Group IV-A of the Periodic Table. More specifically it isintended to cover: germanium, tin, lead and mixtures of these metals. Itis an essential feature of the present invention that substantially allof the Group IV-A metallic component is present in the final catalyst inan oxidation state above that of the elemental metal. In other words,this component may be present in chemical combination with one or moreof the other ingredients of the composite, or as a chemical compound ofthe Group IV-A metal such as the oxide, sulfide, halide, oxyhalide,oxychloride, aluminate, and the like compounds. Based on the evidencecurrently available, it is believed that best results are obtained whensubstantially all of the Group IV-A metallic component exists in thefinal composite in the form of the corresponding oxide such as the tinoxide, germanium oxide, and lead oxide, and the subsequently describedoxidation and reduction steps, that are preferably used in thepreparation of the instant composite, are believed to result in acatalytic composite which contains an oxide of the Group IV-A metalliccomponent. Regardless of the state in which this component exists in thecomposite, it can be utilized therein in any amount which iscatalytically effective, with the preferred amount being about 0.01 toabout 5 wt. % thereof, calculated on an elemental basis, and the mostpreferred amount being about 0.05 to about 2 wt. %. The exact amountselected within this broad range is preferably determined as a functionof the particular Group IV-A metal that is utilized. For instance, inthe case where this component is lead, it is preferred to select theamount of this component from the low end of the range -- namely, about0.01 to about 1 wt. %. Additionally, it is preferred to select theamount of lead as a function of the amount of the platinum groupcomponent as explained hereinafter. In the case where this component istin, it is preferred to select from a relatively broader range of about0.05 to about 2 wt. % thereof. And, in the preferred case, where thiscomponent is germanium the selection can be made from the full breadthof the stated range -- specifically, about 0.01 to about 5 wt. %, withbest results at about 0.05 to about 2 wt. %.

This Group IV-A component may be incorporated in the composite in anysuitable manner known to the art to result in a uniform dispersion ofthe Group IV-A moiety throughout the carrier material such as,coprecipitation or cogellation with the porous carrier material, ionexchange with the carrier material, or impregnation of the carriermaterial at any stage in its preparation. It is to be noted that it isintended to include within the scope of the present invention allconventional procedures for incorporating a metallic component in acatalytic composite, and the particular method of incorporation used isnot deemed to be an essential feature of the present invention so longas the Group IV-A component is uniformly dispersed throughout the porouscarrier material. One acceptable method of incorporating the Group IV-Acomponent into the catalytic composite involves cogelling the Group IV-Acomponent during the preparation of the preferred carrier material,alumina. This method typically involves the addition of a suitablesoluble compound of the Group IV-A metal of interest to the aluminahydrosol. The resulting mixture is then commingled with a suitablegelling agent, such as a relatively weak alkaline reagent, and theresulting mixture is thereafter preferably gelled by dropping into a hotoil bath as explained hereinbefore. After aging, drying and calciningthe resulting particles there is obtained an intimate combination of theoxide of the Group IV-A metal and alumina. One preferred method ofincorporating this component into the composite involves utilization ofa soluble decomposable compound of the particular Group IV-A metal ofinterest to impregnate the porous carrier material either before, duringor after the carrier material is calcined. In general, the solvent usedduring this impregnation step is selected on the basis of its capabilityto dissolve the desired Group IV-A compound without effecting the porouscarrier material which is to be impregnated; ordinarily, good resultsare obtained when water is the solvent; thus the preferred Group IV-Acompounds for use in this impregnation step are typically water-solubleand decomposable. Examples of suitable Group IV-A compounds are:germanium difluoride, germanium tetra-alkoxide, germanium dioxide,germanium tetrafluoride, germanium monosulfide, tin chloride, tinbromide, tin dibromide di-iodide, tin dichloride di-iodide, tinchromate, tin difluoride, tin tetrafluoride, tin tetraiodide, tinsulfate, tin tartrate, lead acetate, lead bromate, lead chlorate, leadchloride, lead citrate, lead formate, lead lactate, lead malate, leadnitrate, lead nitrite, lead dithionate, and the like compounds. In thecase where the Group IV-A component is germanium, a preferredimpregnation solution is germanium tetrachloride dissolved in anhydrousalcohol. In the case of tin, tin chloride dissolved in water ispreferred. In the case of lead, lead nitrate dissolved in water ispreferred. Regardless of which impregnation solution is utilized, theGroup IV-A component can be impregnated either prior to, simultaneouslywith, or after the other metallic components are added to the carriermaterial. Ordinarily, best results are obtained when this component isimpregnated simultaneously with the other metallic components of thecomposite. Likewise, best results are ordinarily obtained when the GroupIV-A component is germanium oxide or tin oxide.

Regardless of which Group IV-A compound is used in the preferredimpregnation step; it is essential that the Group IV-A metalliccomponent be uniformly distributed throughout the carrier material. Inorder to achieve this objective when this component is incorporated byimpregnation, it is necessary to maintain the pH of the impregnationsolution at a relatively low level corresponding to about 7 to about 1or less and to dilute the impregnation solution to a volume which is atleast approximately the same or greater than the volume of the carriermaterial which is impregnated. It is preferred to use a volume ratio ofimpregnation solution to carrier material of at least 1:1 and preferablyabout 2:1 to about 10:1 or more. Similarly, it is preferred to use arelatively long contact time during the impregnation step ranging fromabout 1/4 hour up to about 1/2 hour or more before drying to removeexcess solvent in order to insure a high dispersion of the Group IV-Ametallic component in the carrier material. The carrier material is,likewise, preferably constantly agitated during this preferredimpregnation step.

A second essential ingredient of the subject catalyst is the platinumgroup component. That is, it is intended to cover the use of platinum orpalladium or iridium or rhodium or osmium or ruthenium or mixturesthereof as a second component of the present composite. It is anessential feature of the present invention that substantially all of theplatinum group component exists within the final catalytic composite inthe elemental metallic state (i.e., as elemental platinum or palladiumor iridium etc.). Generally the amount of the second component used inthe final composite is relatively small compared to the amount of theother components combined therewith. In fact, the platinum groupcomponent generally will comprise about 0.01 to about 2 wt. % of thefinal catalytic composite, calculated on an elemental basis. Excellentresults are obtained when the catalyst contains about 0.05 to about 1wt. % of platinum, iridium or palladium metal.

This platinum group metal component may be incorporated in the catalyticcomposite in any suitable manner known to result in a relatively uniformdistribution of this component in the carrier material such ascoprecipitation or cogellation, ion-exchange, or impregnation. Thepreferred method of preparing the catalyst involves the utilization of asoluble, decomposable compound of a platinum group metal to impregnatethe carrier material in a relatively uniform manner. For example, thiscomponent may be added to the support by commingling the latter with anaqueous solution of chloroplatinic, chloroiridic or chloropalladic acid.Other water-soluble compounds of platinum group metals may be employedby impregnation solutions and include ammonium chloroplatinate,bromoplatinic acid, platinum dichloride, platinum tetrachloride hydrate,platinum dichlorocarbonyl dichloride, dinitrodiaminoplatinum, tetramineplatinum chloride, palladium chloride, palladium nitrate, palladiumsulfate, etc. The utilization of a platinum group metal chloridecompound, such as chloroplatinic, chloroiridic or chloropalladic acid,is ordinarily preferred. Hydrogen chloride, nitric acid or the like acidis also generally added to the impregnation solution in order to furtherfacilitate the uniform distribution of the platinum group componentthroughout the carrier material. In addition, it is generally preferredto impregnate the carrier material after it has been calcined in orderto minimize the risk of washing away the valuable platinum or palladiumcompounds; however, in some cases it may be advantageous to impregnatethe carrier material when it is in a gelled state.

Another essential ingredient of the instant catalyst is a Group IV-Btransition metal component. Elements included within the scope of thisexpression are chromium, molybdenum and tungsten, with tungsten beingespecially preferred. This component may exist within the final catalystcomposite in any form wherein substantially all of the Group VI-B metalmoiety is present in an oxidation state above that of the correspondingmetal such as in a compound like the corresponding oxide, sulfide,halide, oxyhalide, aluminate, or in chemical combination with one ormore of the other ingredients of the composite. Best results areobtained when substantially all of this component is present in thecomposite as the corresponding Group VI-B metal oxide. It is preferredthat the final composite contain about 0.01 to about 3 wt. % of thiscomponent, calculated on an elemental basis with the most preferredrange being about 0.05 to about 1 wt. %. A particularly preferredcatalyst, for example, would contain, on an elemental basis, about 0.05to about 1 wt. % tungsten. The function performed by this component isnot entirely understood; however, I believe its prime influence is thatit acts in conjunction with the Group IV-A metallic component to promoteand stabilize the platinum group component.

This Group VI-B transition metal component may be incorporated in thefinal composite in any suitable manner known to those skilled in thecatalyst formulation art which results in a relatively uniformdispersion of the Group VI-B moiety in the carrier material. One methodinvolves impregnation of the porous carrier material with a suitablesolution of the Group VI-B transition metal at any stage in thepreparation of the carrier material -- that is, either as a hydrogel orafter its calcination. Another metal is the ion-exchange method in whicha solution of a suitable compound of the Group IV-B transition metal,wherein the metal is present as an exchangeable ion, is contacted withthe carrier material. Still another method involves cogellation orcoprecipitation of the Group IV-B component with the carrier material.The preferred method involves impregnation of the calcined carriermaterial with a solution containing the Group IV-B transition metal; forexample, excellent results are obtained by impregnating with aqueoussolution of a suitable Group VI-B compound such as ammonium tungstate,sodium tungstate, metatungstic acid, molybdenum tetrabromide, molybdicacid, chromium dibromide, chromium dichloride, chromic acid, chromiumnitrate, sodium chromate, ammonium molybdate, etc., followed byconventional drying and calcination or oxidation steps. Like theprevious components, this component may be added before, during or afterthe addition of the other metallic components, with best resultsobtained with simultaneous addition. For example, in the case of thepreferred platinum-germanium-tungsten catalyst, excellent results areobtained with an impregnation solution comprising a mixture of a firstsolution containing chloroplatinic acid, nitric acid, and ammoniumtungstate with a second solution containing germanium tetrachloridedissolved in anhydrous ethanol.

A highly preferred ingredient of the catalyst used in the presentinvention is the alkali or alkaline earth component. More specifically,this component is selected from the group consisting of the compounds ofthe alkali metals--cesium, rubidium, potassium, sodium, and lithium--andof the alkaline earth metals--calcium, strontium, barium, and magnesium.This component exists within the catalytic composite in an oxidationstate above that of the elemental metal such as a relatively stablecompound such as the oxide or sulfide, or in combination with one ormore of the other components of the composite, or in combination withthe carrier material such as, for example, in the form of an alkali oralkaline earth metal aluminate. Since, as is explained hereinafter, thecomposite containing the alkali or alkaline earth component is alwayscalcined or oxidized in an air atmosphere before use in the conversionof hydrocarbons, the most likely state this component exists in duringuse in the dehydrogenation reaction is the corresponding metallic oxidesuch as lithium oxide, potassium oxide, sodium oxide, and the like.Regardless of what precise form in which it exists in the composite, theamount of this component utilized is preferably selected to provide anonacidic composite containing about 0.1 to about 5 wt. % of the alkalimetal or alkaline earth metal, and, more preferably, about 0.25 to about3.5 wt. %. Best results are obtained when this component is a compoundof lithium or potassium. The function of this component is to neutralizeany of the acidic material such as halogen which may have been used inthe preparation of the present catalyst so that the final catalyst isnonacidic.

This alkali or alkaline earth component may be combined with the porouscarrier material in any manner known to those skilled in the art toresult in a relatively uniform dispersion of this component throughoutthe carrier material with consequential neutralization of any acidicsites wich may be present therein. Typically good results are obtainedwhen it is combined by impregnation, coprecipitation, ion-exchange, andthe like procedures. The preferred procedure, however, involvesimpregnation of the carrier material either before, during, or after itis calcined, or before during, or after the other metallic ingredientsare added to the carrier material. Best results are ordinarily obtainedwhen this component is added to the carrier material after the othermetallic components because the alkali metal or alkaline earth metalcomponent acts to neutralize the acid or materials used in the preferredimpregnation procedure for these metallic components. In fact, it ispreferred to add the platinum group, Group IV-A and Group VI-Bcomponents to the carrier material, oxidize the resulting composite in anet air stream at a high temperature (i.e. typically about 600° to 1000°F.), then treat the resulting oxidized composite with steam or a mixtureof air and steam at a relatively high temperature of about 800° to about1050° F. in order to remove at least a portion of any residual acidityand thereafter add the alkali metal or alkaline earth component.Typically, the impregnation of the carrier material with this componentis performed by contacting the carrier material with a solution of asuitable decomposable compound or salt of the desired alkali or alkalineearth metal. Hence, suitable compounds include the alkali metal oralkaline earth metal halides, sulfate, nitrates, acetates, carbonates,phosphates, and the like compounds. For example, excellent results areobtained by impregnating the carrier material after the other metalliccomponents have been combined therewith, with an aqueous solution oflithium nitrate or potassium nitrate.

Regarding the preferred amounts of the various metallic components ofthe subject catalyst, I have found it to be an essential practice tospecify the amounts of the Group VI-B component as a function of theamount of the platinum group component. On this basis, the amount of theGroup VI-B component is selected from the ranges previously specified sothat the atomic ratio of Group VI-B metal to the platinum group metalcontained in the composite is about 0.05:1 to 4:1, with best resultsobtained when the range is about 0.1:1 to about 1:1. Similarly, it is apreferred practice to select the amount of the Group IV-A metalliccomponent to produce a composite containing an atomic ratio of GroupIV-A metal to platinum group metal within the broad range of about0.05:1 to 10:1. However, for the Group IV-A metal to platinum groupmetal ratio, the best practice is to select this ratio on the basis ofthe following preferred ranges for the individual Group IV-A species:(1) for germanium, it is about 0.3:1 to 10:1, with the most preferredrange being about 0.6:1 to about 6:1; (2) for tin, it is about 0.1:1 to3:1, with the most preferred range being about 0.5:1 to 1.5:1; and, (3)for lead, it is about 0.5:1 to 0.9:1, with the most preferred rangebeing about 0.1:1 to 0.75:1. Similarly, the amount of the alkali oralkaline earth component is ordinarily selected to produce a compositehaving an atomic ratio or alkali metal or alkaline earth metal toplatinum group metal of about 5:1 to about 50:1 or more, with thepreferred range being about 10:1 to about 25:1.

Another significant parameter for the instant catalyst is the "totalmetals content" which is defined to be the sum of the platinum groupcomponent, the Group IV-A metallic component, the Group VI-B component,and the alkali or alkaline earth component, calculated on an elementalmetal basis. Good results are ordinarily obtained with the subjectcatalyst when this parameter is fixed at a value of about 0.2 to about 5wt. %, with best results ordinarily achieved at a metals loading ofabout 0.4 to about 4 wt. %.

Integrating the above discussion of each of the essential and preferredcomponents of the catalytic composite used in the present invention, itis evident that an especially preferred nonacidic catalytic compositecomprises a combination of a platinum group component, a Group IV-Ametallic component, a Group VI-B transition metal component, and analkali or alkaline earth component with an alumina carrier material inamounts sufficient to result in the composite containing on an elementalbasis, from about 0.05 to about 1 wt. % platinum group metal, about 0.05to about 2 wt. % Group IV-A metal, about 0.05 to 1 wt. % Group VI-Bmetal, about 0.25 to about 3.5 wt. % of the alkali metal or alkalineearth metal, and an atomic ratio of Group VI-B metal to platinum groupmetal of about 0.1:1 to about 4:1.

Regardless of the details of how the components of the catalyst arecombined with the porous carrier material, the resulting multimetalliccomposite generally will be dried at a temperature of about 200° F. toabout 600° F. for a period of from about 2 to about 24 hours or more,and finally calcined or oxidized at a temperature of about 600° F. toabout 1100° F. in an air atmosphere for a period of about 0.5 to 10hours, preferably about 1 to about 5 hours, in order to convertsubstantially all the metallic components to the corresponding oxideform. When acidic components are present in any of the reagents used toeffect incorporation of any one of the components of the subjectcomposite, it is a good practice to subject the resulting composite to ahigh temperature treatment with steam or with a mixture of steam andair, either before, during or after this oxidation step in order toremove as much as possible of the undesired acidic component. Forexample, when the platinum group component is incorporated byimpregnating the carrier material with chloroplatinic acid, it ispreferred to subject the resulting composite to a treatment with steamor a mixture of steam and air at a temperature of about 600 to about1100° F. in order to remove as much as possible of the undesiredchloride.

It is an essential feature of the present invention that the resultantoxidized catalytic composite is subjected to a substantially water-freeand hydrocarbon-free reduction step prior to its use in the conversionof hydrocarbons. This step is designed to selectively reduce theplatinum group component to the elemental metallic state and to insure auniform and finely divided dispersion of the metallic componentsthroughout the carrier material, while maintaining substantially all ofthe Group IV-A and Group VI-B components in a positive oxidation state.It is a good practice to dry the oxidized catalyst prior to thisreduction step by passing a stream of dry air or nitrogen through arange at a temperature of about 500 to 1100° F. and at a GHSV of about100 to 800 hr.⁻¹ until the effluent stream contains less than about 1000ppm. H₂ O and preferably less than 500 ppm. Preferably substantiallypure and dry hydrogen (i.e. less than 20 vol. ppm. H₂ O) is used as thereducing agent in this reduction step. The reducing agent is contactedwith the oxidized catalyst at conditions including a temperature ofabout 800° F. to about 1200° F., a GHSV of about 300 to 1000 hr.⁻¹, anda period of time of about 0.5 to 10 hours effective to reducesubstantially all of the platinum group component to the elementalmetallic state while maintaining the Group IV-A and Group VI-Bcomponents in an oxidation state above that of the elemental metal. Thisreduction treatment may be performed in situ as part of a start-upsequence if precautions are taken to predry the plant to a substantiallywater-free state and if substantially water-free and hydrocarbon-freehydrogen is used.

The resulting selectively reduced catalytic composite may, in somecases, be beneficially subjected to a presulfiding operation designed toincorporate in the catalytic composite from about 0.05 to about 0.5 wt.% sulfur, calculated on an elemental basis. Preferably, thispresulfiding treatment takes place in the presence of hydrogen and asuitable sulfur-containing sulfiding reagent such as hydrogen sulfide,lower molecular weight mercaptans, organic sulfides, etc. Typically,this procedure comprises treating the selectively reduced catalyst witha sulfiding reagent such as a mixture of hydrogen and hydrogen sulfidehaving about 10 moles of hydrogen per mole of hydrogen sulfide atconditions sufficient to effect the desired incorporation of sulfur,generally including a temperature ranging from about 50° F. up to about1100° F. or more. It is generally a good practice to perform thispresulfiding step under substantially water-free conditions. It iswithin the scope of the present invention to maintain or achieve thesulfided state of the instant catalyst during use in the conversion ofhydrocarbons by continuously or periodically adding a decomposablesulfur-containing compound, such as the ones previously mentioned, tothe reactor containing the catalyst in an amount sufficient to provideabout 1 to 500 wt. ppm., preferably 1 to 20 wt. ppm. of sulfur based onhydrocarbon charge.

According to the method of the present invention, the dehydrogenatablehydrocarbon is contacted with the multimetallic catalytic compositedescribed above in a dehydrogenation zone maintained at dehydrogenationconditions. This contacting may be accomplished by using the catalyst ina fixed bed system, a moving bed system, a fluidized bed system, or in abatch type operation; however, in view of the danger of attrition lossesof the valuable catalyst and of well-known operational advantages, it ispreferred to use a fixed bed system. In this system, the hydrocarbonfeed stream is preheated by any suitable heating means to the desiredreaction temperature and then passed into a dehydrogenation zonecontaining a fixed bed of the catalyst previously characterized. It is,of course, understood that the dehydrogenation zone may be one or moreseparate reactors with suitable heating means therebetween to insurethat the desired conversion temperature is maintained at the entrance toeach reactor. It is also to be noted that the reactants may be contactedwith the catalyst bed in either upward, downward, or radial flow fashionwith the latter being preferred. In addition, it is to be noted that thereactants may be in the liquid phase, a mixed liquid-vapor phase, or avapor phase when they contact the catalyst, with best results obtainedin the vapor phase.

Although hydrogen is the preferred diluent for use in the subjectdehydrogenation method, in some cases other art-recognized diluents maybe advantageously utilized such as steam, methane, carbon dioxide, andthe like diluents. Hydrogen is preferred because it serves thedual-function of not only lowering the partial pressure of thedehydrogenatable hydrocarbon, but also of suppressing the formation ofhydrogen-deficient, carbonaceous deposits on the catalytic composite.Ordinarily, hydrogen is utilized in amounts sufficient to insure ahydrogen to hydrocarbon mole ratio of about 1:1 to about 20:1, with bestresults obtained in the range of about 1.5:1 to about 10:1. The hydrogenstream charged to the dehydrogenation zone will typically be recycledhydrogen obtained from the effluent stream from this zone after asuitable hydrogen separation step. When utilizing hydrogen in theinstant process, improved results are obtained if water or awater-producing substance (such as an alcohol, ketone, ether, aldehyde,or the like oxygen-containing decomposable organic compound) is added tothe dehydrogenation zone in an amount calculated on the basis ofequivalent water, corresponding to about 50 to about 10,000 wt. ppm. ofthe hydrocarbon charge stock, with about 1500 to 5000 wt. ppm. of watergiving best results.

Regarding the conditions utilized in the process of the presentinvention, these are generally selected from the dehydrogenationconditions well known to those skilled in the art for the particulardehydrogenatable hydrocarbon which is charged to the process. Morespecifically, suitable conversion temperatures are selected from therange of about 700° to about 1200° F. with a value being selected fromthe lower portion of this range for the more easily dehydrogenatedhydrocarbons such as the long chain normal paraffins and from the higherportion of this range for the more difficultly dehydrogenatedhydrocarbons such as propane, butane, and the like hydrocarbons. Forexample, for the dehydrogenation of C₆ to C₃₀ normal paraffins, bestresults are ordinarily obtained at a temperature of about 800° to about950° F. The pressure utilized is ordinarily selected at a value which isas low as possible consistent with the maintenance of catalyst stabilityand is usually about 0.1 to about 10 atmospheres with best resultsordinarily obtained in the range of about 0.5 to about 3 atmospheres. Inaddition, a liquid hourly space velocity (calculated on the basis of thevolume amount, as a liquid, of hydrocarbon charged to thedehydrogenation zone per hour divided by the volume of the catalyst bedutilized) is selected from the range of about 1 to about 40 hr.⁻¹, withbest results for the dehydrogenation of long chain normal paraffinstypically obtained at a relatively high space velocity of about 25 to 35hr.⁻¹.

Regardless of the details concerning the operation of thedehydrogenation step, an effluent stream will be withdrawn therefrom.This effluent will usually contain unconverted dehydrogenatablehydrocarbons, hydrogen, and products of the dehydrogenation reactions.This stream is typically cooled and passed to a hydrogen-separating zonewherein a hydrogen-rich vapor phase is allowed to separate from ahydrocarbon-rich liquid phase. In general, it is usually desired torecover the unreacted dehydrogenatable hydrocarbon from thishydrocarbon-rich liquid phase in order to make the dehydrogenationprocess economically attractive. This recovery operation can beaccomplished in any suitable manner known to the art such as by passingthe hydrocarbon-rich liquid phase through a bed of suitable adsorbentmaterial which has the capability to selectively retain thedehydrogenated hydrocarbons contained therein or by contacting same witha solvent having a high selectivity for the dehydrogenated hydrocarbon,or by a suitable fractionation scheme where feasible. In the case wherethe dehydrogenated hydrocarbon is a mono-olefin, suitable adsorbentshaving this capability are activated silica gel, activated carbon,activated alumina, various types of specially prepared zeoliticcrystalline aluminosilicates, molecular sieves, and the like adsorbents.In another typical case, the dehydrogenated hydrocarbons can beseparated from the unconverted dehydrogenatable hydrocarbons byutilizing the inherent capability of the dehydrogenated hydrocarbons toeasily enter into several well known chemical reactions such asalkylation, oligomerization, halogenation, sulfonation, hydration,oxidation, and the like reactions. Irrespective of how thedehydrogenated hydrocarbons are separated from the unreactedhydrocarbons, a stream containing the unreacted dehydrogenatablehydrocarbons will typically be recovered from this hydrocarbonseparation step and recycled to the dehydrogenation step. Likewise, thehydrogen phase present in the hydrogen-separating zone will be withdrawntherefrom, a portion of it vented from the system in order to remove thenet hydrogen make, and the remaining portion is typically recycledthrough suitable compressing means to the dehydrogenation step in orderto provide diluent hydrogen therefor.

In a preferred embodiment of the present invention wherein long chainnormal paraffin hydrocarbons are dehydrogenated to the correspondingnormal mono-olefins, a preferred mode of operation of this hydrocarbonrecovery step involves an alkylation reaction. In this mode, thehydrocarbon-rich liquid phase withdrawn from the hydrogen-separatingzone is combined with a stream containing an alkylatable aromatic andthe resulting mixture passed to an alkylation zone containing a suitablehighly acid catalyst such as an anhydrous solution of hydrogen fluoride.In the alkylation zone the mono-olefins react with alkylatable aromaticwhile the unconverted normal paraffins remain substantially unchanged.The effluent stream from the alkylation zone can then be easilyseparated, typically by means of a suitable fractionation system, toallow recovery of the unreacted normal paraffins. The resulting streamof unconverted normal paraffins is then usually recycled to thedehydrogenation step of the present invention.

The following working examples are introduced to illustrate further thenovelty, mode of operation, utility, and benefits associated with thedehydrogenation method and nonacidic multimetallic catalytic compositeof the present invention. These examples of specific embodiments of thepresent invention are intended to be illustrative rather thanrestrictive.

These examples are all performed in a laboratory scale dehydrogenationplant comprising a reactor, a hydrogen separating zone, heating means,cooling means, pumping means, compressing means, and the likeconventional equipment. In this plant, the feed stream containing thedehydrogenatable hydrocarbon is combined with a hydrogen streamcontaining water in an amount corresponding to about 2000 wt. ppm. ofthe hydrocarbon feed and the resultant mixture heated to the desiredconversion temperature, which refers herein to the temperaturemaintained at the inlet to the reactor. The heated mixture is thenpassed into contact with the instant multimetallic catalyst which ismaintained as a fixed bed of catalyst particles in the reactor. Thepressures reported herein are recorded at the outlet from the reactor.An effluent stream is withdrawn from the reactor, cooled, and passedinto the hydrogen-separating zone wherein a hydrogen gas phase separatesfrom a hydrocarbon-rich liquid phase containing dehydrogenatedhydrocarbons, unconverted dehydrogenatable hydrocarbons, and a minoramount of side products of the dehydrogenation reaction. A portion ofthe hydrogen-rich gas phase is recovered as excess recycle gas with theremaining portion being continuously recycled, after water addition asneeded, through suitable compressing means to the heating zone asdescribed above. The hydrocarbon-rich liquid phase from the separatingzone is withdrawn therefrom and subjected to analysis to determineconversion and selectivity for the desired dehydrogenated hydrocarbon aswill be indicated in the Examples. Conversion numbers of thedehydrogenatable hydrocarbon reported herein are all calculated on thebasis of disappearance of the dehydrogenatable hydrocarbon and areexpressed in mole percent. Similarly, selectivity numbers are reportedon the basis of moles of desired hydrocarbon produced per 100 moles ofdehydrogenatable hydrocarbon converted.

All of the catalysts utilized in these examples are prepared accordingto the following general method with suitable modification instoichiometry to achieve the compositions reported in each example.First, an alumina carrier material comprising 1/16 inch spheres havingan apparent bulk density of about 0.3 g/cc is prepared by: forming analumina hydroxyl chloride sol by dissolving substantially pure aluminumpellets in a hydrochloric acid solution, adding hexamethylenetetramineto the resulting alumina sol, gelling the resulting solution by droppingit into an oil bath to form spherical particles of an alumina hydrogel,aging, and washing the resulting particles with an ammoniacal solutionand finally drying, calcining, and steaming the aged and washedparticles to form spherical particles of gamma-alumina containingsubstantially less than 0.1 wt. % combined chloride. Additional detailsas to this method of preparing this alumina carrier material are givenin the teachings of U.S. Pat. No. 2,620,314.

The resulting gamma-alumina particles are then contacted at suitableimpregnation conditions with an aqueous impregnation solution comprisinga mixture of two precursor solutions: the first an aqueous solutioncontaining chloroplatinic acid, ammonium tungstate, and nitric acid andthe second an alcoholic solution prepared by dissolving germaniumtetrachloride in anhydrous alcohol and thereafter aging the resultingsolution until an equilibrium condition is established therein. Theamounts of metallic reagents contained in this impregnation solution arecarefully adjusted to yield a final multimetallic catalytic compositecontaining a uniform dispersion of the desired amounts of platinum,tungsten and germanium. The nitric acid is utilized in an amount ofabout 5 wt. % of the alumina particles. In order to ensure a uniformdispersion of the metal moieties in the carrier material, theimpregnation solution is maintained in contact with the carrier materialparticles for about 1/2 hour at a temperature of about 70° F. withconstant agitation. The impregnated spheres are then dried at atemperature of about 225° F. for about an hour and thereafter calcinedor oxidized in an air atmosphere containing about 5 to 25 vol. % H₂ O ata temperature of about 500° F. to about 1000° F. for about 2 to 10 hourseffective to convert all of the metallic components to the correspondingoxide forms. In general, it is a good practice to thereafter treat theresulting oxidized particles with an air stream containing about 10 toabout 30% steam at a temperature of about 800° F. to about 1000° F. foran additional period of about 1 to about 5 hours in order to reduce anyresidual combined chloride contained in the catalyst to a value of lessthan 0.5 wt. % and preferably less than 0.2 wt. %. In the cases shown inthe examples where the catalyst utilized contains an alkali or alkalineearth component, this component is added to the oxidized andsteam-treated multimetallic catalyst in a separate impregnation step.This second impregnation step involves contacting the oxidizedmultimetallic catalyst with an aqueous solution of a suitabledecomposable salt of the alkali or alkaline earth component underconditions selected to result in a uniform dispersion of this componentin the carrier material. For the catalyst utilized in the presentexamples, the salt is either lithium nitrate or potassium nitrate. Theamount of the salt of the alkali metal utilized is chosen to result in afinal catalyst having the desired nonacidic characteristics. Theresulting alkali or alkaline earth impregnated particles are thenpreferably dried, oxidized, and steamed in an air atmosphere in much thesame manner as is described above following the first impregnation step.In some cases, it is possible to combine both of these impregnationsteps into a single step, thereby significantly reducing the time andcomplexity of the catalyst manufacturing procedure.

The resulting oxidized catalyst is therefter subjected to a drying stepwhich involves contacting the oxidized particles with a dry air streamat a temperature of about 1050° F., a GHSV of 300 hr.⁻¹ for a period ofabout 10 hours. The dried catalyst is then purged with a dry nitrogenstream and thereafter selectively reduced by contacting with a dryhydrogen stream at conditions including a temperature of about 870° F.,atmospheric pressure and a gas hourly space velocity of about 500 hr.⁻¹for a period of about 1 to 10 hours effective to reduce substantiallyall of the platinum component to the elemental metallic state whilemaintaining substantially all of the tungsten, germanium and alkali oralkaline earth components in a positive oxidation state.

EXAMPLE I

The reactor is loaded with 100 cc of a catalyst containing, on anelemental basis, 0.375 wt. % platinum, 0.2 wt. % germanium, and 0.1 wt.% tungsten, and less than 0.15 wt. % chloride. The feed stream utilizedis commercial grade isobutane containing 99.7 wt. % isobutane and 0.3wt. % normal butane. The feed stream is contacted with the catalyst at atemperature of 1065° F., a pressure of 10 psig., a liquid hourly spacevelocity of 4.0 hr.⁻¹, and a hydrogen to hydrocarbon mole ratio of 2:1.The dehydrogenation plant is lined-out at these conditions and a 20 hourtest period commenced. The hydrocarbon product stream from the plant iscontinuously analyzed by GLC (gas liquid chromatography) and a highconversion of isobutane is observed with a high selectivity forisobutylene.

EXAMPLE II

The nonacidic catalyst contains, on an elemental basis, 0.375 wt. %platinum, 0.3 wt. % germanium, 0.2 wt. % tungsten, 0.6 wt. % lithium,and 0.15 wt. % combined chloride. The feed stream is commercial gradenormal dodecane. The dehydrogenation reactor is operated at atemperature of 870° F., a pressure of 10 psig., a liquid hourly spacevelocity of 32 hr.⁻¹, and a hydrogen to hydrocarbon mole ratio of 8:1.After line-out period, a 20 hour test period is performed during whichthe average conversion of the normal dodecane is maintained at a highlevel with a selectivity for normal dodecene of about 90%.

EXAMPLE III

The nonacidic catalyst is the same as utilized in Example II. The feedstream is normal tetradecane. The conditions utilized are a temperatureof 840° F., a pressure of 20 psig., a liquid hourly space velocity of 32hr.⁻¹, and a hydrogen to hydrocarbon mole ratio of 8:1. After a line-outperiod, a 20 hour test shows an average conversion of about 12%, and aselectivity for normal tetradecene of about 90%.

EXAMPLE IV

The nonacidic catalyst contains, on an elemental basis, 0.375 wt. %platinum 0.25 wt. % germanium, 0.1 wt. % tungsten, and 0.6 wt. %lithium, with combined chloride being less than 0.2 wt. %. The feedstream is substantially pure cyclohexane. The conditions utilized are atemperature of 950° F., a pressure of 100 psig., a liquid hourly spacevelocity of 3.0 hr.⁻¹, and a hydrogen to hydrocarbon mole ratio of 5:1.After a line-out period, a 20 hour test is performed with almostquantitative conversion of cyclohexane to benzene and hydrogen.

EXAMPLE V

The catalyst contains, on an elemental basis, 0.6 wt. % platinum, 0.2wt. % germanium, 0.2 wt. % tungsten, 1.5 wt. % potassium, and less than0.2 wt. % combined chloride. The feed stream is commercial gradeethylbenzene. The conditions utilized are a pressure of 15 psig., aliquid hourly space velocity of 32 hr.⁻¹, a temperature of 1050° F., anda hydrogen to hydrocarbon mole ratio of 8:1. During a 20 hour testperiod, 85% or more of equilibrium conversion of the ethylbenzene isobserved. The selectivity for styrene is about 95%.

It is intended to cover by the following claims, all changes andmodifications of the above disclosure of the present invention whichwould be self-evident to a man of ordinary skill in thecatalyst-formulation art or in the hydrocarbon dehydrogenation art.

I claim as my invention:
 1. A nonacidic catalytic composite comprising aporous carrier material containing, on an elemental basis, about 0.01 toabout 2 wt. % platinum group metal, about 0.01 to about 5 wt. % GroupIV-A metal, about 0.01 to about 3 wt. % Group VI-B transition metal andabout 0.1 to about 5 wt. % alkali metal or alkaline earth metal; whereinthe platinum group metal, Group IV-A metal, Group VI-B transition metal,and alkali metal or alkaline earth metal are uniformly dispersedthroughout the porous carrier material; wherein substantially all of theplatinum group metal is present in the elemental metallic state; whereinsubstantially all of the Group IV-A, Group VI-B transition metal, andalkali metal or alkaline earth metal are present in an oxidation stateabove that of the elemental metal; and wherein the atomic ratio of GroupVI-B transition metal to platinum group metal is about 0.05:1 to about4:1.
 2. A nonacidic catalytic composite as defined in claim 1 whereinthe platinum group metal is platinum.
 3. A nonacidic catalytic compositeas defined in claim 1 wherein the platinum group metal is palladium. 4.A nonacidic catalytic composite as defined in claim 1 wherein theplatinum group metal is iridium.
 5. A nonacidic catalyst composite asdefined in claim 1 wherein the porous carrier material is a refractoryinorganic oxide.
 6. A nonacidic catalytic composite as defined in claim5 wherein the refractory inorganic oxide is alumina.
 7. A nonacidiccatalytic composite as defined in claim 1 wherein the Group IV-A metalis germanium.
 8. A nonacidic catalytic composite as defined in claim 1wherein the Group IV-A metal is lead.
 9. A nonacidic catalytic compositeas defined in claim 1 wherein the Group IV-A metal is tin.
 10. Anonacidic catalytic composite as defined in claim 1 wherein the GroupVI-B transition metal is tungsten.
 11. A nonacidic catalytic compositeas defined in claim 1 wherein the Group VI-B transition metal ismolybdenum.
 12. A nonacidic catalytic composite as defined in claim 1wherein the Group VI-B transition metal is chromium.
 13. A nonacidiccatalytic composite as defined in claim 1 wherein the alkali metal oralkaline earth metal is potassium.
 14. A nonacidic catalytic compositeas defined in claim 1 wherein the alkali metal or alkaline earth metalis lithium.
 15. A nonacidic catalytic composite as defined in claim 1wherein the composite contains, on an elemental basis, about 0.05 toabout 1 wt. % platinum group metal, about 0.05 to about 2 wt. % GroupIV-A metal, about 0.05 to about 1 wt. % Group VI-B transition metal, andabout 0.25 to about 3.5 wt. % alkali metal or alkaline earth metal. 16.A nonacidic catalytic composite as defined in claim 1 wherein the metalscontent thereof is adjusted so that the atomic ratio of Group IV-A metalto platinum group metal is about 0.05:1 to about 10:1 and the atomicratio of alkali metal or alkaline earth metal to platinum group metal isabout 5:1 to about 50:1.
 17. The nonacidic catalytic composite of claim1 in sulfided form and containing about 0.05 to about 0.5 wt. % sulfur.